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ゆりなひでやま
7 years ago
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1 Haskell ( ) kazu@iij.ad.jp 1

2 2

3 Blub Paul Graham Blub Blub Blub Blub 3

4 Haskell Sebastian Sylvan Haskell 4

5 Java Joel Spolsky Scheme Haskell C Java 2 5 Java 5

6 Haskell Haskell 98 Language and Libraries The Revised Report Haskell Glasgow Haskell Compiler 6

7 ( ) 7

8 Haskell 8 2 8

9 9

10 (1) for ($i=0; $i<10; $i++) { print "$i\n"; } mapm_ print [0..9] $i = 0; while (<>) { $i++ } print "$i\n" print. length. lines =<< getcontents 10

$print "$i\n" print. length.$

11 (2) for ($i = 1; $i <= $n; $i++) { $ret = $ret * $i; } fact n = if n == 1 then 1 else n * fact (n-1) fact 1 = 1 fact n = n * fact (n-1) 11

12 How What 12

13 What 13

14 (1) qsort [] = [] qsort (p:ps) = qsort less ++ [p] ++ qsort more where less = filter (<p) ps more = filter (>=p) ps qsort [5,7,3,8,1,9,2,4,0,6] qsort [3,1,2,4,0] ++ [5] ++ qsort [7,8,9,6] qsort (p:ps) = qsort [x x<-ps,x<p] ++ [p] ++ qsort [x x<-ps,x>=p] O(N 2 ) 14

15 (2) primes = sieve [2..] sieve (p:ps) = p : sieve ps where notmultiplep n = n mod p /= 0 ps = filter notmultiplep ps seieve [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 ] 2:seive [3,5,7,9,11,13,15 ] 2:3:seive [5,7,11,13 ] sieve (p:ps) = p : sieve [n n <- ps, n mod p /= 0] 15

16 John Hughes ( ) 16

17 even 2 True filter even [0..9] [0,2,4,6,8] map even [0..5] [True,False,True,False,True,False] Haskell oddlist = filter odd oddlist [0..9] [1,3,5,7,9] 17

18 Haskell 2 div 0 *** Exception: divide by zero func x y = x func 1 (2 div 0) 1 Unix % grep keyword file wc -l length $ filter even [1..100] 18

19 ) replicate replicate * 5 "*****" replicate c 0 = [] replicate c n = c : replicate c (n-1) repeat * [ *, *, *, *, *, ] take 5 [ *, *, *, *, *, ] [ *, *, *, *, * ] "*****" replicate c n = take n $ repeat c 19

20 Haskell? 20

21 decomp : " foo : bar : baz " ["foo","bar","baz"] break break (== : ) " foo : bar : baz " (" foo ", ": bar : baz ") (1) split c cs = case break (==c) cs of (w,"") -> [w] (w,_:cs ) -> w:split c cs _ : c split : " foo : bar : baz " [" foo "," bar "," baz "] 21

22 dropwhile isspace " foo " "foo " break isspace "foo " ("foo"," ") fst ("foo"," ") "foo" (2) trim cs = fst $ break isspace $ dropwhile isspace cs trim " foo " "foo" decomp c cs = map trim $ split c cs decomp : " foo : bar : baz " ["foo","bar","baz"] 22

23 23

24 data Bool = True False data Maybe a = Just a Nothing data Either a b = Left a Right b 24

25 Haskell 25

26 123 + data Op = Plus Multi deriving Show data Exp = Leaf Int Node Op Exp Exp deriving Show Node Plus (Leaf 1) (Node Multi (Leaf 2) (Leaf 3)) 26

27 flatten f l@(leaf a) = f l flatten f n@(node o e1 e2) = flatten f e1 ++ f n ++ flatten f e2 op (Leaf _) = [] op (Node o ) = [o] flatten op $ Node Plus (Leaf 1) (Node Multi (Leaf 2) (Leaf 3)) [Plus,Multi] 27

28 Haskell filter map 28

29 Haskell if then else then else [0,1,2,3] [False,True,2,3] (void *) 29

30 putstrln :: String -> IO () (++) :: [a] -> [a] -> [a] main = putstrln "Hello, " ++ "World!\n" (putstrln "Hello, ") ++ "World!\n" ++ (++) :: IO() -> [Char] -> [Char] main = putstrln $ "Hello, " ++ "World!\n" 30

31 31

32 Haskell 32

33 33

34 2 return >>= bind >>= Haskell cat getcontents :: IO String putstr :: String -> IO () main = getcontents >>= \cs -> putstr cs IO IO IO 34

35 do >>= main = getcontents >>= \cs -> putstr cs do main = do cs <- getcontents putstr cs YES Haskell Haskell Parsec 35

36 Perl Perl Perl ($1 ) Yacc/lex Yacc/lex C C 36

37 Parsec >>= Haskell Haskell 37

38 [+-]?[1-9][0-9]* plus = do char + return id minus = do char - return negate noneof xs = do c <- oneof xs return $ digittoint c -- number = do pm <- plus < > minus < > return id d <- noneof " " ds <- many(noneof " ") return $ pm $ foldl tonum 0 (d:ds) where tonum x y = x * 10 + y 38

haskell.gby

haskell.gby Haskell 1 2 3 Haskell ( ) 4 Haskell Lisper 5 Haskell = Haskell 6 Haskell Haskell... 7 qsort [8,2,5,1] [1,2,5,8] "Hello, " ++ "world!" "Hello, world!" 1 + 2 div 8 2 (+) 1 2 8 div 2 3 4 map even [1,2,3,4]